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Patented July 2, 192 9.'

UNITED STATES PATENT OFFICE.

GEORGE D. CHAMBERLAIN, OF ASHLAND, KENTUCKY, ASSIGNOR '10 R. '1. VANDERIBIL'I. COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PIGKLING OF METALS.

No Drawing.

This invention relates to the pickling and cleaning of metals, and particularly to the pickling of iron or steel, to remove scale therefrom, although the invention is of more or less general application to the cleaning or pickling of metals such as iron or steel for the removal of oxides or scale therefrom.

The pickling or cleaning of iron or steel is commonly effected by means of acid pickling 10 or cleaning baths which remove the scale or oxide from the metal; The pickling baths commonly employed are acid baths which often attack the metal as well as the scale. This action on the metal is'undesirable and objectionable, involving not only excessive consumption of acids, but also corrosion or dissolving of metal and tending to give a rough or pitted surface.

The present lnvention provides an improved bath for pickling and cleaning metals and also an improved process of pickling or cleaning the metal in which the acid pickling bath has incorporated therein a small amount of an inhibiting amine.

I have found that the addition of a small amount of'certain amines prevents or retards or inhibits the attack of the acid pickling bath on the metal without interfering with the removal of scale or oxide by the acid bath.

or pickling bath, according to the present invention, include various of the amines which produce this inhibiting efiect. Among these may be mentioned dibenzylaniline O H EN OH -C 5) 2a certain amines together with other com;

pounds such as dibenzylaniline and thiocarbanilid.

The acid pickling baths with which the agents mentioned are used may be acid baths such as are commonly employed for pickling or cleaning iron and steel, containing for exv ample about ten percent of sulfuric acid. .1

Such baths are gradually impoverished by the action of the acid in removing the scale or rust and their content of ferrous sulfate increases until the bath becomes too weak or The agents which are added to the cleaning Application filed February 19, 1927. Serial No. 189,673.

too concentrate -l in ferrous sulfate for further 7 use. Instead of using sulfuric acid baths, other acid baths can be used, including acid sulfate baths. I

The amount of the inhibiting amine added to the bath for carrying out the pickling or cleaning operation can be varied. In general, only a small amount of such a compound is required, for example, a small fraction of one percent. In the case of dibenzylaniline, for

example, about two-to five pounds of the compound can be employed for each ton of sixty degree Baum acid used in the pickling bath. A pickling bath including the same percentage of any of the other inhibiting amines mentioned above likewise gives satlsfactory results.

The carrying out of the pickling or cleaning operation may be the same as in ordinary practice. Forexample,thepicklingcanbecarried out continuously by passing the material to be pickled, such as wire or sheets, through a number of baths in a regulated manner; or by immersing the article to be pickled in the pickling bath for a suitable period of time. The temperature of the bath can be varied, ordinarily being around 150 to 180 F. The pickling bath may be replenished by the addition of further amounts of acid until the iron sulfate reaches too great a concentration. The addition of the inhibiting amine to the bath prevents or retards or inhibits the action of the acid bath on the metal without interfering with the removal of scale or oxide. The formation of hydrogen by the action of the acid bath on the metal is also' reduced and the production of acid mist or fumes also greatly reduced. There is also a saving in the acid I as well as a protection of the metal. The reduced amount of action of the acid on the 90 metal and the reduction in amount of hydrogen produced correspondingly reduces the amount of hydrogen absorbed b the metal. The employment of the inhibiting amine in the pickling or cleaning operation, according to the present invention, involves'but small additional expense and results in advantages in operation,

economy of acid, protection of the metal from attack, etc., which materially improve the pickling and cleaning operation. In the claims the word amine is used in a strict sense and refers to nitrogenous compounds in which the nitrogen is linked to hydrocarbon radicals, 5i alkyl, aryl, aralkyl, etc-as distingui from amides in which one bond of the nitrogen is satisfied by I I l an acid group, such as the C 0 group 1n acetamide or the G S in thioui'ea.

I claim:- 1. The method-of cleaning or pickling metals which comprises subjecting the same to a non-oxidizing mineral acid pickling or cleaning bath and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide. and thereby reducing the formation of hydrogen and the production of acid mist and efi'ecting an economy in the acid consumed, by incorporat ing in the acid bath a small amount of an inhibiting amine.

2. The method of pickling or cleaning iron or steel which comprises subjecting the same to an acid pickling bath containing sulrfuric acid and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide. and thereby reducing the formation of hydrogen and the production of acid mist and effecting an economy in the acid consumed. by incorporating in the acidbath a small fraction of one per cent of an inhibiting'amine.

3. The method of cleaning or pickling metacid and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide, and thereby reducing the formation of hydrogen and the production of acid mist and effecting an economy in the acid consumed. by incorporating in the acid bath a small fraction of one per cent of dibenzylaniline.

5. The method of cleaning or pickling mettals which comprisessubjecting the same to a non-oxidizing mineral acid pickling-or cleanlng bath and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide. and thereby reducing the formation of hydrogen and the production ofacid mist and efiecting an economy in the acid consumed, by incorporating in the acidbath a small a'mount of an inhibiting amine containing the group N R in which R is an aralkyl radical.

6. The method of cleaning or pickling metals which comprises subjecting the same to a non-oxidizing mineral acid pickling or cleaning bath and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide, and thereby reducing the formation of hydrogen and the production of acid mist and eliecting an economy in the acid consumed, by incorporating in the acid bath a small amount of an inhibiting amine of the formula R NR' where R is an aralkyl radical and R is an aromatic radical or hydrogen.

7. The method of cleaning or pickling metals which comprises subjecting the same-to a non-oxidizing mineral acid pickling or cleaning bath and inhibiting the chemical action of the acid on the metal without interfering withthe removal of scale or oxide, and thereby reducing the formation of hydrogen and the production of acid mist and effecting an economy in the acid consumed, by incorporating in the acid bath a small amount of an inhibiting amine of the formula-R. .NR' where R is an aralkyl radical and R is an aryl radical.

8. The method of cleaning or pickling metals which comprisessubjecting the same to a non-oxidizing mineral acid pickling or cleaning bath and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide. and thereby reducing the formation of hydrogen and the production of acid mist and effecting an economy in the acid consumed. by incorporating in the acid bath a small amount of a dibenzylated amine. I

9. The method of pickling or cleaning iron or steel which comprises subjecting the same to an acid pickling bath containing sulfuric acid and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide. and thereby reducing the formation of hydrogen and the production of acid mist and efiecting an economyin the acid consumed, by incorporating in the acid bath a small fraction of cent of dibenzylamine.

10. The method of-cleaning or pickling metals which comprises subjecting the same to a nonoxidizing mineral acid pickling or,

cleaning bath and inhibiting the chemical action of the acid on the metal without interfering with the removal of scale or oxide, and thereby reducing the formation of hydrogen and the production of acid mist and effecting an economy in the acid consumed.

by incorporating in the acid bath a small amount of dibenzylaniline together with thiecarbanilid.

11. The method of pickling or cleaning iron or steel which comprises subjecting the same to an acid pickling bath containing sulfuric aci and inhibiting the chemical action of the acid on the metal without interfering with the removal of scaleor oxide. and thereby reducing the formation of hydrogen and the production of acid mist and efi'ecting an economy in the acid consumed. by incorporating in the acid bath a small fraction of one one per v per cent of dibenzylaniline together with pickling or cleaning metals containing a thiocarbanilid. small amount of an amine containing the 12. A non-oxidizing mineral acid bath for group -NR in which R is an aralkyl radi- 15 pickling or cleaning metals containing a cal. 5 small amount of an inhibiting amine. 16. A non-oxidizing mineral acid bath for 13. A bath for pickling or cleaning metals pickling or cleaning metals containing a containing sulphuric acid and a small fracsmall amount of an inhibiting amine of the 'tion of one per cent of an inhibiting amine. formula R NR where R is an aralkyl radical 14. A non-oxidizing mineral acid bath for and R is an aryl radical. pickling or cleaning metals containing a In testimony whereof I aflix my signature.

small amount ofa dibenzylated amine.

15. A non-oxidizing mineral acid bath for GEORGE D. CHAMBERLAIN. 

